Cirno’s Perfect Math Class

IOSYS’s latest creation revolves around Cirno‘s stupidity. Animation is by TETLA POT and the song is part of IOSYS’s latest album 東方氷雪歌集. I can’t say I’m an avid Touhou follower, but I like IOSYS’s renditions and some of the characters have grown on me.

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Cirno’s problem:A bus leaves Scarlet Mansion with three people on board.
One person gets off at Hakugyokurou and half a person gets on.
At Yakumo’s house, two people get off.
How many people are left on the bus?